An early manifestation of infection with HIV-1 is the loss of helper T (CD4+) cell function. Subsequently these cells are also depleted in number cue to cytopathic effects of HIV-1. Since CD4+ are required in antibody responses to protein antigens, deficiency in function or number of these cells would be expected to result in impaired antibody responses against HIV-1. Our approach for developing a vaccine to boost immune responses in HIV-1 infected individuals has been to use T-cell independent (TI) antigens and thus bypass he requirement for CD4+ T cells. It is known that Brucella abortus (BA) can be used a carrier for haptens to stimulate antibody responses in the absence of T cells. Previously we showed that HIV-1 conjugated to Brucella abortus (BA) elicited anti-HIV antibody responses even in mice depleted od CD4+ T cells. Since lipopolysaccharide (LPS) from other gram negative bacilli can stimulate B cells, we decided to purify LPS from BA which, if active could replace BA as the carrier. This would refine the use of BA as a carrier to a molecule of defined structure and eliminate other BA elements that may be toxic. LPS from BA was purified by butanol extraction and characterized by KDO, protein and nucleic acid content. It was also tested for functional activity. LPS-BA behaved as T-independent type I carrier since (i) it was effective in stimulating mouse spleen cells to proliferate and to secrete antibody even after T cell depletion; and (ii) TNP-LPS (BA) could induce anti-TNP antibodies of all IgG subclasses.